Wireless telecommunications systems are known. In a cellular system, radio coverage is provided to user equipment, for example, mobile telephones, in areas known as cells. A base station is located in each cell to provide radio coverage. User equipment in each cell receives information and data from a base station and transmits information and data to the base station.
Information and data transmitted by a base station to the user equipment typically occurs on channels of radio carriers known as “downlink” carriers. Information and data transmitted by user equipment to a base station occurs on uplink data channels of radio carriers known as “uplink” carriers.
Functionality of user equipment operating in a CELL_FACH state has been enhanced by implementation of various sub-features. Two such sub-features are: (i) standalone HS-DPCCH transmission and (ii) RACH fallback.
A HS-DPCCH (High Speed-Dedicated Physical Control Channel) is a channel used by user equipment on the uplink to carry control information, such as CQI (Channel Quality Index) and acknowledgements for downlink HS-DSCH (High Speed-Dedicated Shared Channel) packets. The HS-DPCCH (or feedback channel) allows feedback information to be transmitted back to a base station so that appropriate transport block sizes can be chosen, on the basis of CQI information, and so that blind retransmissions can be minimized as a result of ack/nack messaging.
According to the RACH fallback sub-feature, user equipment operating in a CELL_FACH state is operable to request allocation of a common or shared channel, for example an E-DCH (Enhanced-Dedicated Channel) resource. If user equipment is operating within a cell of a network which is experiencing congestion and the common channels are being heavily used, there may be no common resource available for allocation to that user equipment. The RACH fallback sub-feature allows a base station to operate to indicate to user equipment requesting common resource that it should “fall back” to operate using a Random Access Channel (RACH) for uplink transmissions.
It will be appreciated that the co-existence of the RACH fallback sub-feature and the standalone feedback sub-feature can lead to conflict in operation at user equipment.
Aspects aim to resolve conflict between sub-features without impacting overall network operation.